1. Field of the Invention
The invention relates to multiorifice structures and a method of fabrication and, more particularly, to a multiorifice disc for use in conjunction with an automotive type fuel injector valve for atomizing the fuel injected into an internal combustion engine.
2. Prior Art
The use of multiorifice plates or discs in conjunction with nozzles for dispersing or atomizing an exiting fluid is well known in the art. Such multi aperture structures are found in a wide variety of applications ranging from old-fashioned sprinkling cans for watering flowers to sophisticated fuel injector valves for internal combustion engines. Whether the multi apertured structure merely disperses the fluid as with the sprinkling can or atomizes the fluid as is desirable in the automotive fuel injector application, depends upon several factors, one of which is the size and shape of the individual apertures, as well as the force with which the liquid is ejected. For fuel atomizing applications, small holes in the range from several hundred to less than one hundred microns range appear to be best suited. Various techniques for making such multi apertured structures are known in the art. Because of the size of the holes, drilling or punching the individual apertures is generally not considered because costs would be prohibitive for competitive, high production applications. Alternate techniques are photoetching or fusion of small diameter tubes, such as taught by Roberts et al. in U.S. Pat. No. 3,737,367 (June 1973). Because of the depth of the holes required, fabrication of the multi aperture structure using photoetching techniques is quite complex and usually requires etching from both sides to obtain the required uniformity of the holes. The tubular approach taken by Roberts et al. appears to be the better of the two methods, but in this process the tubes must be filled to prevent the individual tubes from collapsing. Therefore, a subsequent etching step is required to etch out the filled holes. Further, the orifices produced by the Roberts et al technique are generally circular in configuration. However, the orifices may have a hexagonal configuration, as taught by Varian et al. in U.S. Pat. No. 2,619,438 (Nov. 25, 1972) using a similar technique.
Experimental evidence indicates that better atomization can be achieved from triangular or other nonsymmetrical orifices where surface tension forces cause the exiting or ejected fluid to vibrate at higher frequencies and, therefore, break up into smaller particles.
The disclosed invention is a method for producing a multiorifice structure which parallels to some extent the method taught by Roberts et al which results in a multiorifice structure having noncircular apertures, has greater structural strength, and superior atomizing capabilities.
In the disclosed invention, the interstices between geometrically stacked rods form the orifices of the multiorifice structure. The basic concept of using the interstial spaces between wires as a fluid passageway is taught by Fassler in U.S. Pat. No. 3,602,620 (August 1971). In this patent, the interstices between the wires form a passageway for oxygen gas in a thermal lance. The thermal lance has a relatively long length to diameter ratio and the wires are twisted to impede the oxygen flow.